The present invention relates to a transmitter-receiver system for use in an audio equipment which comprises a transmitter unit installed in the audio equipment to transmit its output signal, and a receiver unit installed in an earphone to receive transmitted signal from the transmitter unit.
In order not to interfere with others while listening the music of an audio equipment, an earphone shall be used. However, when an earphone is used and connected to the output terminal of the audio equipment, the limitation of the length of the electric wire of the earphone, the movement of the user is confined to a limited area. Furthermore, when an audio equipment is installed, the electric wires between the amplifier and the speakers may be disorderly exposed to the outside. If to keep the electric wires from sight, the installation cost of the audio equipment will be high.
The present invention has been accomplished to provide a transmitter-receiver system which eliminates the afore said problems. It is one object of the present invention to provide a transmitter-receiver system which can be installed in the amplifier and speakers of an audio equipment so that the sound signal of the amplifier can be transmitted to the speakers for output wirelessly. It is another object of the present invention to provide a transmitter-receiver system which can be installed in an audio equipment and an earphone so that the user can listen to the music of the audio equipment without interfering then with other persons. It is still another object of the present invention to provide a transmitter-receiver system which eliminates the use of a complidated  complicated matching device by using an inductance type transmitting antennae which reduces the floating frequency. It is still another object of the present invention to provide a transmitter-receiver system which consumes low voltage. It is still another object of the present invention to provide and transmitter-receiver unit which automatically cuts off battery power supply when the audio equipment does no  not work. It is still another object of the present invention to provide a transmitter-receiver unit which adopts a dual oscillation frequency regulating circuit for the transmitter unit as well as the receiver unit so that the range of frequency can be broadly adjusted without being limited by the installation of a SAW did  in conventional methods in which the output of the first intermediate frequency can be within the range of 10.7MH to 100MH; the second frequency mixing and the second local oscillation may be eliminated when desired. It is still another object of the present invention which allows  to allow the user (consumer) to charge  change the frequency of the first local oscillation through VR1 without changing the frequency of the second local oscillation.
According to the preferred embodiment of the present invention.  the transmitter unit comprises an automatic electric level regulator to regulate the electric level of the output signal of audio equipment to a predetermined range. , a power control circuit controlled by the output signal of the audio equipment to provide the necessary working voltage. , and an inductance antennae to transmit an output signal from the audio equipment to the receiver unit. The receiver unit comprises an automatic 24-time frequency divider circuit to effectively discriminate left and right sound tracks. and , an auto-shut off circuit to automatically to cut off the power supply when the audio equipment does not work. Furthermore, the transmitter unit and the receiver unit further use a respective external and internal dual oscillation  oscillatory frequency regulating circuit consisting of an oscillating transistor. , a dialectic resonator. , and two variable resistors for regulating the range of the frequency.